In the current IP local area network, an address of a layer-2 network is obtained by adopting an ARP (Address Resolution Protocol) in IPV4 and adopting a NDP (Neighbor Discovery Protocol) in IPV6. Mechanisms for address discovery are substantially identical for both the ARP and the NDP, i.e., both the ARP and the NDP obtain a data link layer address corresponding to a destination IP address by means of layer-2 broadcasting. For an Ethernet, the data link layer address corresponds to a MAC (Media Access Control) address. Each host maintains a standalone buffer, and presets aging timing time; and when sending an IP message, the host has to broadcast an ARP/NDP message in the local area network to query the data link layer address corresponding to the destination IP address if this destination IP address is not recorded in the local buffer of the host.
When there are a large number of hosts in the local area network, for example, a large-scale data center, or even a cross-region L2VPN (layer-2 virtual private network) connected using L2VPN technology, there may be thousands of or tens of thousands of hosts; and this situation may be worse when using the application of virtualization technology. With the virtualization technology, one physical host can support dozens of virtual hosts, and will be able to support up to hundreds of virtual hosts in the future. Each virtual host has its own IP address and MAC address. Although isolation of broadcast storm can be implemented using VLAN (virtual local area network) division (where VLAN includes port-based VLAN and MAC-based VLAN), both of the port-based VLAN and the MAC-based VLAN cannot be used since the virtual machine migration technology brought by virtualization technology requires the host itself, the IP address and the MAC address to be completely floatable.
A very important function in the virtualization technology is to achieve load balance and energy conservation and emission reduction using the virtual machine migration. The application scenes are as follows: 1) when services are busy, if load of a data center 1 is too high and is close to an overload threshold, while a data center 2 is still in a light load state, a virtual machine management center instructs a plurality of virtual machines in the data center 1 to migrate to a physical server in the data center 2, thereby reducing the load of the data center 1; 2) when services are not busy, all virtual machines on some physical servers are migrated to other physical servers with light load which may be within the same data center or may be at another data center site, and after migration, the physical centers from which the virtual machines are migrated are powered off, thereby achieving the function of energy conservation and emission reduction.
Under the existing technology system, since for the virtual machine migration the current state of service connection of the operation system needs to be kept, the IP and MAC addresses should remain unchanged after migration. However, since other hosts/virtual machines communicating with the migrated virtual machines have MAC buffers, the message forwarding relationship has actually changed after the virtual machines migrate across the sites, and these MAC buffers will cause communication interrupt; a layer-2 switch also needs to perform the MAC address learning again, and if the virtual machines migrate to the different port of the switch within the same site, the process of studying the MAC address again will also cause the communication interrupt.